Slide track for machine tools



W. HEER SLIDE TRACK FOR MACHINE TOOLS July 23, 1957 2 Sheets-Sheet 1 Filed July 1, 1954 I IN VEN TOR Walt er He er APcorneys tates Hit 2300,375 srmn TRACK non MACHINE Toots Walter Hear, Zurich, Switzerland, assignor to Escher Wyss Aktiengesellschaft, Zurich, Switzerland, a corporation of Switzerland This invention relates to a slide track for machine tools, mainly for heavy loads.

With slide tracks of the hitherto known types of construction, it is either not possible with large loads and small sliding speeds to obtain pure liquid friction between the slide track and the body sliding thereon, or if liquid friction is obtained, only such small thicknesses of lubrication film are obtained that considerable viscosity forces are set up transversely of the film owing to the great drop in speed. Consequently, a comparatively large output is necessary for driving the machine tool, particularly at heavy loads.

The invention has for its object to reduce the power consumption for the movement of the sliding body, as compared with the hitherto known constructional forms of slide tracks.

According to the invention, this is achieved by the fact that a slide track for machine tools presents at its surface a plurality of recesses arranged distributed therein and forming between the slide track and the sliding body chambers surrounded by guide tracks, and that a plurality of lubricant feeds are each separately connected to at least one of these chambers, each of the said feeds supplying such a quantity of lubricant under pressure to the said chambers that a gap of sufiicient width for ensuring liquid friction by lubricant discharging I therethrough is formed between the guide tracks and the sliding body. In this way liquid friction with minimum friction loss both in the rest position and also at any sliding speed is attained.

One embodiment of the subject of the invention is shown in simplified form as an example in the accompanying drawing, wherein:

Figure 1 is a plan view of the circular slide tracks of a vertical lathe,

Figure 2 is a radial section through the outer slide track and the part sliding thereon, taken on the line II-II of Figure 1,

Figure 3 is a corresponding section through a slide track, which also comprises a guideway for a counterholcling bar,

Figure 4 is a section in the sliding direction through a pressure chamber according to the line IV-IV of Figure 1, and

Figure 5 shows a complete arrangement of the lubricating means for the slide track of a vertical lathe.

The mounting of the face plate of a vertical lathe comprises, according to Figure 1, an inner slide track 1 and an outer slide track 2.. Eight pressure chambers 3 are provided in the inner slide track and thirty-two such chambers 4 are provided in the outer slide track, said pressure chambers being formed by recesses at the surfaces of the slide tracks. The pressure chambers 4 are surrounded by guide tracks 2 Four lubricant feed devices 5 are each separately connected to a group of two pressure chambers 3 of the inner slide track, and eight lubricant supply devices 6 are each separately connected {mat 2,8903 Patented July 23, 1957 2 to a group of four pressure chambers 4 of the outer slide track. Each of the lubricant supply devices of the inner slide track is supplied with lubricant by a separate pump 7 and each of the lubricant supply devices of the outer slide track is supplied with lubricant by a separate pump 8.

By means of the pumps 7 and 8, each of the feed devices 5 and 6, respectively, and the pressure chambers 3 and 4, respectively, connected thereto and filled with lubricant, is supplied with such a quantity of lubricant that the lubricant discharging between the guide tracks and the sliding part forms a lubricant film of adequate thickness for ensuring the liquid friction with minimum friction loss, both in the rest position and also at any sliding speed.

Figure 2 represents a section to a larger scale through the outer slide track and that part of the face plate which is sliding thereon. This part of the face plate is indicated at 9. A slip lining 11 is fixed on this part 9 by means of screws 10. The lubricant passes from the associated lubricant feed device 6 through a connecting pipe 12 and a passage 13 into the pressure chamber 4.

Since a prescribed quantity of liquid is now supplied by the associated pump 8, the sliding part 9 is lifted by the pressure of the liquid to such an extent that the lubricant is able to discharge through gaps 14 between the guide'tracks 2 and the sliding part 9 into collecting ducts 15 of the slide track 2, in order from thence to be supplied again to the lubricant collecting vessel (not shown), from which the pumps withdraw their delivery quantity. The pumps supply their entire output through the lubricant feed devices to the pressure chambers, so that the lubricant pressure is adjusted in accordance with the prevailing load of the slide surface.

The output of the pumps is made so large that the sliding part 9 is lifted to such an extent that the gap 14 is given a sufficient width and thus a lubricant film of sufficient thickness is formed for ensuring liquid friction with minimum friction loss. As well as discharging radially outwards and inwards, the lubricant naturally also discharges tangentially from the chambers 4, it then being deflected radially outwards or inwards in the zone between the chambers.

The most favourable action in the sense of reducing the friction losses is produced by the fact that the weight of the sliding part is mainly supported by the lubricant pressure in the chambers and thus the lubricant films in the gaps 14 are relieved. Practically no friction forces occur in the pressure chambers, and the sliding part is lifted by the liquid pressure to such an extent that also in the gaps 14, the lubricant film is sufiiciently thick in order to obtain smallest possible frictional losses. These gaps act as throttle points for the medium under pressure and automatically regulate the pressure in the pressure chambers 4. The guide tracks 2 thus serve less as slide surfaces than as stabilising surfaces for the sliding part, which in this case, in contrast to slide tracks of hitherto known construction, is supported mainly on the liquid buffer contained in the pressure chambers and not on the lubricant films between the sliding surfaces.

The pressure chambers may be constructed as uniform depressions in the slide track. As will be seen from Figures 1 and 4, the pressure chambers in this case are fashioned as depressions of the slide track, which chambers are tapered in an area 16 in the sliding direction. By means of this construction of the limitation of the pressure chambers, the result can be obtained that with the movement of the part disposed above the slide track, lubricant is drawn into the tapered or wedge-shaped gap, whereby a supplementary pressure is produced in this area. The pressure chambers themselves are thus somewhat relieved, so that the pumps only have to continue i body 18, also comprises aguideway for a count'erholding bar 20 connected by screws 191'to the'sliding body. Pressure chambers 21 filled with lubricant are arranged in the supporting surface in the manner described with reference to Figures 1 and 2 in connection with the pressure chambers 4. The pressure liquid is supplied through bores 22 and flows on the one hand into a collecting duct 23 and on the other hand into a chamber 24, in order to pass from the latter through bores 25 into a' collecting duct 26.

A plurality of pressure chambers 27 filled with lubricant are also arranged distributed in the guide surface for the counterholding bar. A plurality of separate lubricant supply devices'28, each ofwhich supplies a predetermined quantity of lubricant, are each connected toat least one of the pressure chambers 27'. The lubricant discharges through the gaps disposed on both sides of the pressure chambers, eitherdirectly or by way of the space 24 through thebores 25 intothe collecting duct 26. The measures described with reference to Figures 1 and 2 are here also transferred to the lubrication of the guide tracks of the counterholding bar.

The counterholding bar prevents too powerful a lifting of the sliding body 18' of the machine tool, whether it be due to the pressure in the chambers 21 or due to external forces. Due to the fact that lubricant is forced into the pressure chambers 27, however, a complete bearing of the counterholding bar on its guide way is prevented. By suitable adaptation of the quantities of lubricant supplied to the pressure chambers 21 and 27, the result can be attained that both the guide tracks of the sliding body 18 and also those of the counterholding bar may be provided with lubricant films of sufficient thickness in order to keep the friction losses small. 7

Instead of the lubricant feed devices being individually equipped with separate pumps, it is also possible for them to emanate from a common feed pipe which is supplied by a single pump. However, in order in this case to arrange that each of the pressure chambers or each of the groups of such chambers is given a quantity of lubricant sufiicient for ensuring liquid friction, means are provided by which the distribution of the output to the individual feed devices is regulated in prescribed manner. Furthermore, it is necessary that the total output of the pump is sufficient'in order to provide all pressure chambers with the quantity of lubricant which is necessary for, attaining liquid friction. It is expedient inthis case to provide a feeler device by which theheight of the sliding part of the machine tool and thus the thickness of the film of lubricant is. measured, and which has a regulating effect on the output of the pump supplying the feed pipe with lubricant, in dependence upon the thickness of the film of lubricant.

Since the quantity of lubricant which is to be supplied to the pressure chamber for maintaining the liquid friction is mainly varied with a change in the sliding speed, it is expedient to provide means by which the quantity of lubricant flowing to the lubricant feed devices is varied in dependence upon the sliding speed in such manner that the thickness of the lubricant film remains substantially constant.

In the rest position and at low speeds, the quantity of lubricant may be kept substantially constant. At higher speeds, on the other hand, the lubricant demand is increased, particularly on account of the heating of the lubricant due to the increased frictional energy and the resultant decrease in the viscosity.

A complete arrangement of the lubrication'means of the slide track of a vertical lathe which satisfies these demands is shown in Figure 5. In this figure, 29 represents the face plate of a vertical lathe, said face plate being guided with a pin 30 in bearings 31 and comprising a sliding part 32. The latter is moved on a slide track 33, which comprises pressure chambers 34 to which the lubricant feed devices 35 are connected. Each of these lubricant feed devices, of which only one is shown in its full length for simplicity of illustration, leads to a pump 36 of the displacement type. These pumps are all driven by a common shaft 37 and draw in lubricant from a container 38. The lubricant discharging from the slide track is led back to the container 38 by way of a pipe 39. A driving motor 40 transmits the turning movement to the face plate 29 of the vertical lathe by way of gear wheels 41, 42, 43, 44. By way of a chain drive 46 and two gear wheels 47 and 48, a further motor 45 drives the pumps 36 at such a speed that the pumps deliver a quantity of lubricant which assures the production of a sufficient thickness of lubricant film when the table is at rest or is turning at slow speed.

The motor 40 is also in communication by way of a chain drive 49 and the gear wheels 47, 48 or three additional gear wheels 50, 51, 52 with the driving shaft 37 of the pumps. Discs 53, 54, 55 with locking pawls are also included in the drive mechanism.

If the face plate 29 is at rest, or if it is rotating only at slow speed, the pumps are driven from the motor 45. The locking pawls of the discs 54 and 55 do not then engage. on the other hand, if the disc 54 is rotating at a higher speed than corresponds to the driving speed due to the motor 45, the gear wheel 47 is driven from the chain drive 49 through the locking pawls of the disc 54, while the locking pawl of the disc 53 slips on the assoc iated ratchet which is now running more slowly.

The drive by way of the disc 55 serves for the drive of the pumps from the driving motor 40, also with reverse rotation of the face plate or the said motor, when a certain speed of rotation is exceeded. In this direction of rotation, the pawl of the disc 54 slips over the ratchet, while the pawl of the disc 55 comes into engagement, if itis being rotated at a higher speed than corresponds to the speed of the pumps when driven by the motor 45.

The result attained by this arrangement is that when the sliding speed is low, i. e. when the speed of the face plate is low, the pumps are driven at constant speed by the motor 45. At high speed, on the other hand, the pumps are driven by the motor 40 at a speed proportional to the sliding speed, i. e. to the number of revolutions of the face plate.

In order tov ensure accurate working of the machine tool, it is necessary to prevent an inclined position of the sliding part of the machine tool. This may be obtained by suitable arrangement of those pressure chambers on the slide track which are provided with separate lubricant feed devices andby suitable regulation of the quantity of lubricant supplied through the individual feed devices. Sufiicient lubricant pressure is supplied, for example, for the said requirements if, in connection with the slide track of a vertical lathe and boring mill, at least three groups of similar pressure chambers are arranged with uniform distribution on the circumference and one lubricant pump of equal output is connected to each of the said groups. The result achieved in this manner is that the loading is uniformly distributed among the three groups, and that consequently the face plate is lifted to the same extent at, alltthree or more positions in order to allow the passage of the prescribed quantity of liquid. An inclined: position of the sliding part is thus prevented.

'With, the slide track according to Figure 1, this object is achieved by the arrangement of four or eight similar groups of pressure chambers in uniformly distributed manner.

With the arrangement which has been illustrated, always only directly adjacent pressure chambers are assembled to. form a group. However, it is also possible for the groups partially to overlap one another, for example, in such manner that the supply pipes of the outermost pressure chambers of two adjacent groups would be interchanged. By means of this step, any irregularities which may be present in the delivery of the individual pumps are balanced more quickly in their action.

The output of the lubricant pumps may also be regulated manually or automatically under the action of other influencing values, instead of in the manner described.

A guide track constructed in accordance with the invention has been described with reference to the drawings in conjunction with a vertical lathe. However, not only circular slide tracks, but also straight slide tracks, for example, for planing machines and milling machines, may be constructed in a corresponding manner. Iri such cases, it is merely necessary to ensure that the sliding part of the machine tool always bears on a plurality of pressure chambers supplied by separate lubricant feed devices. It is however, unimportant if separate pressure chambers or groups of such chambers are uncovered temporarily in the course of the movement. The delivered quantity of liquid then simply discharges Without pressure at those positions.

What is claimed is:

1. In combination a slide track for machine tools comprising a stationary member, a second member capable of transmitting load forces movable relative to said stationary member, said stationary member and said second member having surfaces bearing against each other, one of said bearing surfaces comprising narrow lands delimiting a plurality of pockets; a plurality of lubricant feed devices, each separately connected to at least one of said pockets; pumps of the displacement type, one for each of said lubricant feed devices and separately connected therewith, for supplying lubricant under pressure through said feed devices to said pockets; continuously active lowspeed driving means and driving means having a speed proportional to the sliding speed of said second member; and means serving automatically to connect the said pumps with whichever one of the driving means has the higher speed, so that the pumps are driven at a constant relatively low speed of rotation at low sliding speed of the second member and at relatively higher speeds proportional to said sliding speed when the latter is high.

2. In combination a slide track for machine tools comprising a stationary member, a second member capable of transmitting load forces movable relative to said stationary member, said stationary member and said second member having surfaces bearing against each other, one of said bearing surfaces comprising narrow lands delimiting a plurality of pockets; a plurality of lubricant feed devices, each separately connected to at least one of said pockets; pumps of the displacement type, one for each of said lubricant feed devices and separately connected therewith, for supplying lubricant under pressure through said feed devices to said pockets; and means for driving said pumps at speeds which increase from a chosen minimum as the sliding speed of the second member increases above a chosen value, and for driving said pumps at said minimum when said sliding speed is at or below said chosen value.

References Cited in the file of this patent UNITED STATES PATENTS 603,260 Cook May 3, 1898 2,578,711 Martellotti Dec. 18, 1951 2,731,305 Wiloock Jan. 17, 1956 FOREIGN PATENTS 186,595 Great Britain May 17, 1923 570,984 Great Britain Aug. 1, 1945 

